Signaling system and method



Dec. 28, 1937. R. c. MATHES 2,103,481

" SIGNALYING SYSTEM AND METHOD Filed July 24, 1928 /N [/5 N 70/? Roam r6. M4 THE:

Patented Dec. 28, 1937 ()FFlCE SIGNALING SYSTEM 'AND METHOD Robert C.Mathes, Wyoming, N. J., assignor to Bell Telephone Laboratories,Incorporated, New York, N. Y., a corporation of New York ApplicationJuly 24, 1928, Serial No. 295,057

is Claims.

This invention relates to signaling systems and methods and particularlyto systems and methods for producing images electro-optically.

The. principal object of the invention is to utilize in a novel manner aplurality of transmission lines, such for example as telephone lines, totransmit currents for the production of a television image.

It has been proposed heretofore to scan simultaneously differentportions of a picture or object for producing separate currentscorresponding to the scannings and to transmit these currents overseparate channels. See, for example, Patent No. 1,796,931, of H. E.Ives, granted March 17, 1931.

The type of scanning employed in the preferred embodiment of the presentinvention is that disclosed in a copending application of F. Gray,Serial No. 181,538, filed 'April 6, 1927. This copending applicationdiscloses a scanning arrangement in which a rotating apertured disc isemployed to cause an intensely bright spot of light to sweep across theelemental areas of an object periodically in succession. The lightrefiected from the object impinges on the photosensitive surface of oneor more photoelectric cells for producing an image current.

In accordance with the invention, in its preferred form, energy derivedfrom the image currentproduced by scanning elemental areas insuccession, preferably by the method mentioned just above, is utilizedto control a plurality of transmission lines simultaneously forseparately transmitting energy corresponding to groups of the. elementalareas, respectively. In a somewhat different and specific aspect of theinvention as applied to a television system, a varying electromotiveforce proportional to an image current is impressed on a plurality ofelectric storing elements or condensers, one at a time, at apredetermined rate and the potentials of the charges stored in theseelements are impressed on a transmission channel or channels at a rate.different than said predetermined rate. The electric storing elementsmay be divided into a number of groups and currents corresponding to thepotentials of the charges stored in different groups may betransmittedover different trans mission channels, respectively. Thus amultichannel system may be provided in which the frequency range whichit is required to transmit over each channel is equal to the frequencyrange of the image current produced as a result of scanning divided bythe number of transmission channels employed. These received imageourrent impulses are impressed on. an apparatus for producing an image.While the. image may be produced by causing instantaneous flashes oflight to be emitted from the elemental areas thereof, it is sometimespreferable to sustain the 5 emission of light from each elemental areaso that several or all of the elemental areas emit light at the sametime. This is preferably accomplished by employing, for each elementalarea of the image, a light emitting element which is actuated by thespace current of an electric discharge device and impressing thereceived image current potential corresponding to eachelemental area ona storage element connected to the control electrode of the electricdischarge device for varying its biasing potential, and therefore, thespace current. This is in accordance with features of Patent No.2,058,882, H. E. Ives and R. C. Mathes, granted Oct. 27, 1936, andPatentNo. 2,058,898, of R. C. Mathes. 2

The accompanying drawing, a description of which follows, showsdiagrammatically a television system embodying features of theinvention.

Referring to the drawing, the elemental areas of the field of viewcomprising the subject iii are illuminated in succession along aplurality of parallel lines by light from the source I I passing throughthe spirally arranged apertures in the revolving disc I2. Lightreflected from the successively illuminated elemental areas of thesubject to reaches the light sensitive surface of a photo-electric cell13 and causes the current from the source M- flowing through the celland the resistance IE to vary in amplitude in accordance with theintensity variations of the reflected light. The motor H5 which drivesthe scanning disc l2 also drives the distributor ll, which has aplurality of contacts, one for-each elemental area of the field of viewbeing scanned, and. the distributors It each of which has contactscorresponding to a group of the elemental areas. The rotatable brushesof the distributors l1 and I8 and the disc I2 are mechanically coupledtothe motor l6 and are driven at the same angular velocity.

As the field of view is scanned the varying voltage drop across theresistance l5, corresponding to the tone values of the successiveelemental areas of the field of view, is amplified by the electricdischarge amplifier [9. A plurality of condensers 29, one correspondingto each elemental area of the field of view are provided for storingcharges corresponding to the Varying image current, that is, eachcondenser as it is connected to the anode circuit of the electricdischarge device [9 through the distributor l1 and a blocking condenser31, is charged to a potential corresponding to the potential existingbetween the anode and cathode of the electric discharge device [9 at thetime that the elemental area to which this condenser corresponds isbeing scanned. These condensers are divided into groups and thepotentials to which the condensers of each group are charged areimpressed, through one of the distributors l8, upon a circuit associatedwith one of the transmission channels 2| for causing image current to betransmitted thereover. For example, if the scanning disc is providedwith 50 apertures for scanning the field of view in 50 parallel lineseach of 50 elemental areas, 50 groups of 50 condensers each may beprovided for storing charges corresponding to the tone values of theelemental areas of the field of view and 50 distributors may be providedfor impressing the potentials to which these condensers are charged uponcircuits associated with 50 channels for transmitting the currents whichcontrol the production of the image at the receiving station. The brushof each distributor l8 lags the brush of distributor l1 sufiiciently sothat it completes a circuit to the first charged condenser of the groupwith which it is associ ated soon after this condenser has been chargedthrough the circuit including the brush of distributor H. The potentialsto which the condensers of each group are charged are impressed acrossone of the impedance elements 22 which is preferably largely resistive.This resistance should preferably be high enough so that it does notappreciably discharge the condensers 20 during the time it is associatedwith any one of them. These potentials are impressed between the controlelectrode and cathode of one of the electric discharge amplifiers 36 towhich one of the impedance elements 22 is connected. The anode circuitof each of these electric discharge devices is connected to one of thetransmission channels 2| through a transformer 24. As a resuit a currentwhich varies in amplitude in accordance with the potentials of thesuccessive charges impressed on the condensers 20 of each group ofcondensers is transmitted over the transmission channel 2| associatedwith this group.

At the receiving station there is provided an image producing deviceconsisting of a bank of light emitting elements such as the lamps 25.These elements are preferably arranged in groups corresponding to thegroups of elemental areas of the field of view and the groups ofcondensers at the transmitting station. The image current transmittedover each of the transmission channels 2| is impressed on the primarywinding of one of the transformers 26, the secondary winding of which isconnected to the input circuit of one of the electric dischargeamplifiers 21. The varying potential'across the anode and cathode ofeach electric discharge amplifier 21 is impressed across the condensers28 of one of the groups of condensers through a blocking condenser 29and one of the distributors 30. The distributors 30 are similar to thedistributors I 8 and are driven in synchronism therewith by the motor35. A suitable system such as that disclosed in Patent No. 1,763,909, toH. M. Stoller and E. R. Morton, may be provided for maintaining themotors l6 and 35 in synchronism. The potentials to which the condensers28 are charged are impressed on the control electrodes of the electricdischarge devices 3| for controlling the anode current of these deviceswhich flows from the source of current 32 to the light emitting elements25.

The charging circuits for the condensers 20 should have such a timeconstant that the condensers may be charged to the potential impressedthereon in the time required for scanning a single elemental area of thefield of view. The charging circuits for the condensers 28 should besuch that these condensers can be charged to the potential impressedthereon in the time required for scanning a single elemental areamultiplied by the number of transmission channels employed fortransmitting the image currents. The value of each resistance 33 shuntedacross each condenser 28 is preferably sufliciently high so that chargesare maintained on the condensers 28 without appreciable diminution forat least a considerable portion of the time required for a completescanning of the field of view, this time being preferably of a second orless so that the eye may be given the impression of seeing an object inmotion.

In the system just described there is produced, as a result of scanninga field of view, a single electric current whose amplitude varies inaccordance with the tone values of the elemental areas of the field ofview and energy derived from this current is utilized to control aplurality of transmission channels simultaneously for separatelytransmitting energy corresponding to groups of the elemental areas overthese transmission channels, respectively. The frequency range requiredto be transmitted over 'each of these channels is equal to the entirefrequency range required for image production divided by the number oftransmission channels employed. At the receiving station in this system,the actuation of each element of the image producing apparatus issustained over a period during which the actuation of other elementstakes place. If desired, of course, the actuation of the elements may beinstantaneous. Instead of simultaneously actuating one element from eachof the groups of elements of the image producing device in accordancewith the image current impulses transmitted simultaneously over thep1urality of transmission channels 2|, it is obvious that the receivedimage current impulses may be stored in a plurality of elements and thendistributed to the image producing elements one at a time. It ispossible, of course, to store energy corresponding to the image currentimpulses in mechanical or other devices instead of in condensers.

What is claimed is:

l. The method of television which comprises scanning a plurality ofelemental areas of a field of view one at a time in succession to obtaina single electrical image current and utilizing energy derived from saidcurrent to control a plurality of transmission lines simultaneously.

2. An electro-optical image producing system comprising means forscanning a plurality of elemental areas of a field of view one at a timein succession, a circuit in which is set up an image current as theresult of said scanning, and means for utilizing energy derived fromsaid current to control a plurality of transmission linessimultaneously.

3. An electro-optical image producing system comprising means forproducing a moving beam of light to successively illuminate, one at atime, a plurality of elemental areas of a field of view,

light sensitivemeans for receiving light from each elemental area as itis scanned, a circuit in which is set up an image current as the resultof the light activation of said light sensitive means,and means forutilizing energy derived from said current to control a plurality oftransmission lines simultaneously.

4. In an image producing system, a source of energy characteristic ofthe tone values of successively scanned elemental areas of a field ofView, a plurality of condensers, means for impressing energy from saidsource on said condensers in succession at a predetermined rate, andmeans for utilizing the energy stored in said condensers for producingimpulses of energy in succession at a rate different than saidpredetermined rate for controlling the production of an image of saidfield of view.

5. An electro-optical image producing system comprising means forproducing an electromotive force which varies in accordance with thetone values of successively scanned. elemental areas of a field of view,a plurality of condensers, means for impressing said electromotive forceon said condensers in succession at the rate of scanning the successiveelemental areas for charging them in accordance with the instantaneousvalues of said electromotive force, and means for utilizing the chargesstored in said condensers for producing impulses of electromotive forcein succession at a rate different than said predetermined rate forcontrolling the production of an image of said field of view.

6. The methodof transmitting signaling current, the frequency componentsof which exand transmitting the impulses stored in differentgroups ofcondensers over different transmission channels, respectively at a ratedifferent than said predetermined rate.

'7. The method of transmitting signaling current, the frequencycomponents of which extend over a wide frequency range, over a pluralityof transmission channels, each of which is adapted for transmittingcurrent components extending over only a relatively narrow frequencyrange, which method comprises separately capacitively storing indifferent condensers, respectively, impulses of electromotive forcecorresponding to different instantaneous values of said signalingcurrent insuccession at a predetermined rate, transmitting separategroups of stored impulses over different transmission channels,respectively, the impulses of each group being transmitted at a ratedifferent than said predetermined rate, storing the transmittedimpulses, and producing signals by said stored impulses.

8. In an electro-optical image producing system, means for scanning theelemental areas of an object periodically in succession to produce animage current, a plurality of electrical storing elements, means forimpressing an electromotive force corresponding to said image current onsaid storing elements in succession. at a. predetermined rate, aplurality of transmission channels, means for impressing the componentsof electromotive force stored in different groups of said elements ondifferent transmission channels, respectively, a plurality of electricstoring elements for storing electromotive forces corresponding to saidtransmitted image current components, and an image producing device, theactuation of which is controlled in accordance with the potentials ofthe charges stored in said last-mentioned storingelements.

9. In an image producing system, scanning means for producing energy forcontrolling the production of an image, said scanning means comprisingmeans for illuminating a single olemental area of a field of view at atime, an image producing device comprising a plurality of elementscorresponding to the elemental areas of said field of view, and meansfor utilizing said energy for simultaneously initiating or changing theactuation of a plurality of the elements of said image producing device.

10. An electro-optical image producing system comprising means forilluminating the elemental areas of a field of view one at a time, meansfor producing an image current corresponding to the tone values of thesuccessively illuminated elemental areas, a bank of light emittingelements corresponding to the elemental areas of said field of view, andmeans for utilizing energy derived from said image current forsimultaneously initiating or changing the actuation of a plurality ofsaid light emitting elements.

11. An electro-optical image producing system comprising means includingan apertured rotatable element for scanning a field of view to producean image current which varies in accordance with the tone values of thesuccessively scanned elemental areas of the fieldof view, a plurality oftransmission channels, a plurality of distributors whose rotatablebrushes are mechanically coupled to said rotatable element, one of saiddistributors being employed to impress the image current potential upona plurality of condensers in succession, and the remaining distributorsbeing employed for impressing the potentials of the charges stored ingroups of said condensers upon different transmission channelsrespectively, and means for utilizing the energy transmitted over saidtransmission channels for controlling the production of an image of saidfield of view.

12. An electro-optical image producing system comprising means includingan apertured rotatable element for scanning a field of view to producean image current which varies in accordance with the tone values of thesuccessively scanned elemental areas of the field of view, a pluralityof transmission channels, a plurality of distributors whose rotatablebrushes are mechanically coupled to said rotatable element, one of saiddistributors being employed to impress the image current potential upona plurality of condensers in succession, and the remaining distributorsbeing employed for impressing the potentials of the charges stored ingroups of said condensers onto different transmission channels,respectively, a second group of distributors operating in synchronismwith the aforementioned distributorsfor impressing the image currentsreoeived over said transmission channels onto a plurality of groups ofcondensers, and means controlled in accordance with the charges storedin said last mentioned condensers for controlling production of an imageof said field of View.

13. In an electro-optical image producing system, a bank of condenserelements, means for charging said condenser elements in accordance withthe tone values of different elemental areas, respectively, of a fieldof View, a transmission medium, and means for associating said condenserelements one at a time in succession with said transmission medium overa period of time different from the time required for charging saidcondenser elements in accordance with the tone values of said field ofview.

14'. In an electro-optical image producing system, a bank of electriccapacity elements, means for charging said elements in accordance withthe tone values of difierent elemental areas respectively of a field ofview, a transmission medium, and means for associating said elements oneat a time in succession with said transmission medium over a longerperiod than the period during which the electric capacity elements arebeing charged.

15. The method of electro-optical image production which comprisescapacitively storing in an electric capacitive element at thetransmitting station energy representative of the light tone value of anelemental area of an object, and intermittently associating said elementwith a transmission medium for a period longer than that during whichsaid storing takes place.

16. In an electro-optical image producing apparatus, an electriccapacitive element for storing at the transmitting station energyrepresentative of the light tone values of an elemental area of anobject, a transmission medium, and means for intermittently associatingsaid element with said transmission medium for a period longer than thatduring which said storing takes place.

17. An electro-optical image producing system comprising means forrepeatedly scanning a field of view to produce an image currentwhichvaries in accordance with the tone values of the successively scannedelemental areas of a field of view, each complete scanning taking placewithin the'period of persistence of vision, a plurality of condensers,means for impressing the potential of said image current upon saidcondensers in succession and repeatedly to charge each condenser inaccordance with the tone value of an elemental area of the field ofview, a plurality of transmission channels and means for successivelyimpressing upon one transmission channel the potentials of the chargesstored in the successive condensers of one group of said condensers andfor impressing on another transmission channel the potentials of thecharges stored in the successive condensers of another group of saidcondensers.

18. An electro-optical image producing system comprising means forrepeatedly scanning a field of view to produce an image current whichvaries in accordance with the tone values of the successively scannedelemental areas of a field of View, each complete scanning taking placewithin the period of persistence of vision, a plurality of condensers, adistributor for impressing the potential of said image current upon saidcondensers in succession and repeatedly to charge each condenser inaccordance with the tone value of an elemental area of the field ofview, ,a plurality of transmission channels, a second distributor forsuccessively impressing upon one of said transmission channels thepotentials of the charges stored in the successive condensers of onegroup of said condensers, and

a third distributor for impressing upon another transmission channel thepotentials of the charges stored in the successive condensers of anothergroup of said condensers.

ROBERT C. MATHES.

